Radioactive particle therapy, also known as in vivo gamma knife, is a kind of tumor brachytherapy.In 1974, Stanford University School of Medicine in the United States for the first time applied iodine 125 radioactive particles inter-tissue permanent implantation treatment of unresectable malignant tumors, the effect is exciting. In recent years, radioactive particle implantation therapy has been widely used in developed countries in Europe and the United States, and is adapted to almost all isolated countable malignant solid tumors, with satisfactory results, improving the quality of life of patients and prolonging their survival. Mostly under the guidance of CT, MRI and ultrasound and other imaging equipment, it is the distribution of radioactive particles suitable for tumors to achieve the purpose of brachytherapy. Tumor control probability: the radiation therapy dose is high, its tumor local control rate is high, such as control of subclinical foci need 45-50Gy; microscopic residual foci need 60-65Gy; clinical tumors need 60Gy in T1 stage and 75-80Gy in T4 stage. radioactive particle implantation belongs to the internal radiotherapy technology, from the center of the tumor, from the inside and the outside of the killing, the radiation dose is usually several times of the external radiotherapy, even for the radiation sensitivity, the radioactive particle implantation belongs to the internal radiotherapy technology. The radiation dose is usually several times higher than that of external radiation therapy, so even for pancreatic cancer, which has poor radiation sensitivity, the local treatment effect can be very good. Local treatment dose is high: 125I particle therapy dose: 1: radioactive particle activity: 0.8mci, 0.6mci, 0.4mci 125I particles in the diameter of 8±1mm target area 90% (D90) absorbed dose were: 100, 80, 50GY; 2: prescription dose: the dose of the radical treatment of the tumor that is the prescription dose; 3: the marginal dose of radioactive particles implanted in the tumor should be the prescription dose. The dose i.e. the peripheral margin dose should be the prescription dose. The minimum or lowest dose at the edge of the tumor should also be the prescription dose to ensure that the tumor will not recur, and 90% of the tumor target area gets 90% of the prescription dose to reach the root of the tumor. Small damage to normal tissues, few side effects, long duration of treatment: the effective action of radioactive particles is short (1.7cm), with the increase of the action distance, the radiation attenuates rapidly, and the normal structure around the tumor is protected to the maximum extent. The half-life of Iodine 125 radioactive particles is nearly two months, and the duration of action is more than 10 months, so the implantation is able to kill and maim the tumor in a long-term, continuous and effective way. Small trauma, low pain and good repeatability: image-guided radioactive particle implantation therapy is minimally invasive, performed under local anesthesia, with small trauma, low requirements for patients’ age and physical condition. For local or recurrent or metastatic lesions after particle implantation, the recurrent lesions can be treated again for many times, which controls the lesions, improves the quality of life and prolongs the survival time.